Qt Creator issue : Cannot open include file: ‘windows.h’

Your install directory is:

c:\development\referencebuilds\qt\4.7.4\qt-everywhere-opensource-4.7.4

Let's call it $(QTDIR). Now:

1. Extend your PATH variable to include $(QTDIR)\bin
2. Specify the QMAKESPEC environment variable to be win32-msvc2005
3. Open a Visual Studio command prompt to get the Visual Studio environment variables
4. Run configure
5. Run nmake

This procedure usually gets the Qt build to work for me.

You are probably getting SSL errors which you can handle in a slot. Although not the best final solution, you can use the slot to ignore all SSL errors. I did this by subclassing QWebView:

qwebview.h:

#ifndef WEBVIEW_H
#define WEBVIEW_H

#include <QWebView>

class WebView : public QWebView
{
    Q_OBJECT

    public:
        WebView(QWidget *parent = 0);
    private slots:
        void handleSslErrors(QNetworkReply* reply, const QList<QSslError> &errors);
};

#endif // WEBVIEW_H

qwebview.cpp:

#include "webview.h"
#include <QNetworkReply>
#include <QtDebug>
#include <QSslError>

WebView::WebView(QWidget *parent) :
    QWebView(parent)
{
    load(QUrl("https://gmail.com"));

    connect(page()->networkAccessManager(),
            SIGNAL(sslErrors(QNetworkReply*, const QList<QSslError> & )),
            this,
            SLOT(handleSslErrors(QNetworkReply*, const QList<QSslError> & )));  
}

void WebView::handleSslErrors(QNetworkReply* reply, const QList<QSslError> &errors)
{
    qDebug() << "handleSslErrors: ";
    foreach (QSslError e, errors)
    {
        qDebug() << "ssl error: " << e;
    }

    reply->ignoreSslErrors();
}

main.cpp"

#include <QApplication>
#include "WebView.h"

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    WebView w;
    w.show();
    return a.exec();
}

Running this should produce debug output like this:

handleSslErrors:  
ssl error:  "The host name did not match any of the valid hosts for this certificate" 
ssl error:  "No error" 
ssl error:  "No error" 
...

In your final program, you will of course want to handle SSL errors properly :)